Tetralogy of Fallot in Children
Basics of Tetralogy of Fallot
Tetralogy of Fallot (TOF or "TET") is a rare, complex heart defect that is present at birth (or “congenital”). A problem with the structure of the heart, it changes the normal flow of blood through the heart. The word “tetralogy” refers to four heart defects:
- Ventricular septal defect (VSD). An opening in the dividing wall (or “ventricular septum”) between the two lower chambers of the heart known as the right and left ventricles.
- Pulmonary (or right ventricular outflow tract) obstruction. A muscular obstruction in the right ventricle, just below the pulmonary valve, that decreases normal blood flow. The pulmonary valve may also be abnormally small.
- Overriding aorta. The aorta is shifted toward the right side of the heart so that it sits over the ventricular septal defect.
- Right ventricular hypertrophy. The right ventricle becomes enlarged as it tries to pump blood past the obstruction into the pulmonary artery.
In a normal heart, oxygen-poor (blue) blood returns to the right atrium from the body, travels to the right ventricle, then is pumped through the pulmonary artery into the lungs, where it receives oxygen. Oxygen-rich (red) blood returns to the left atrium from the lungs, passes into the left ventricle, and then is pumped through the aorta out to the body.
In tetralogy of Fallot, blood flow within the heart varies, depending on the size of the ventricular septal defect and severity of the obstruction in the right ventricle.
- With mild right ventricle obstruction, the pressure in the right ventricle can be slightly higher than the left. Some of the oxygen-poor (blue) blood in the right ventricle passes through the VSD to the left ventricle, mixes with the oxygen-rich (red) blood there, and then flows into the aorta. The rest of the oxygen-poor (blue) blood goes its normal route to the lungs. Children with this condition may have slightly lower oxygen levels than normal, but may not appear blue.
- With more serious obstruction in the right ventricle, it is harder for oxygen-poor (blue) blood to flow into the pulmonary artery, so more of it passes through the VSD into the left ventricle, mixes with oxygen-rich (red) blood, and moves out to the body. Children with this condition have lower than normal oxygen levels in the bloodstream, and may appear blue, especially when the pressure in the right ventricle is very high and large amounts of oxygen-poor (blue) blood passes through the VSD to the left side of the heart.
Fast Fact of Tetralogy of Fallot
- According to the National Heart, Lung, and Blood Institute (NHLBI), tetralogy of Fallot affects about 5 of every 10,000 babies and occurs equally in boys and girls.
Causes of Tetralogy of Fallot
Some congenital heart defects may have a genetic link, either occurring due to a gene defect, chromosome abnormality or environmental exposure. Thus some heart problems occur more often in certain families. Maternal abuse of alcohol during pregnancy, leading to fetal alcohol syndrome (FAS), is linked to tetralogy of Fallot. Mothers who take medications to control seizures and mothers with phenylketonuria (PKU) are also more likely to have a baby with tetralogy of Fallot.
Most often this heart defect occurs sporadically (by chance), with no clear cause.
Symptoms of Tetralogy of Fallot
Each child may experience the signs and symptoms of tetralogy of Fallot differently, but common signs and symptoms include:
- A blue color of the skin, lips and nail beds that occurs with activities such as crying or feeding
- Irritability or lethargy due to a decreased amount of oxygen in the bloodstream
- Pale or ashen skin color
- Cool, clammy skin
Because symptoms of tetralogy of Fallot may resemble other medical conditions or heart problems, it’s important to consult with a child's physician for a diagnosis.
Tests, Procedures and Diagnosis of Tetralogy of Fallot
When a child's physician hears a heart murmur during a physical examination, the physician may refer the child to a pediatric cardiologist, who specializes in the diagnosis and treatment of congenital heart defects and heart problems that may develop later in childhood. To make a diagnosis, a cardiologist performs a physical examination, listens to the child’s heart and lungs, and makes other observations. Heart murmurs are evaluated on the basis of pitch, loudness and duration, which give the cardiologist an initial idea of which heart problem a child may have. Diagnostic testing for congenital heart disease varies by a child's age and clinical condition, and may include:
- Chest X-ray. This diagnostic test uses X-ray beams to produce digital images of internal tissues, bones and organs.
- Electrocardiogram (ECG or EKG). This test records the electrical activity of the heart, shows abnormal rhythms (arrhythmias or dysrhythmias) and detects heart muscle stress.
- Echocardiogram (or “echo”). This procedure evaluates the structure and function of the heart by using sound waves recorded on an electronic sensor that produce a moving picture of the heart and its valves.
- Cardiac catheterization. This invasive procedure gives very detailed information about the structures inside the heart. Under sedation, a small, thin, flexible tube (catheter) is inserted into a blood vessel in the groin, and gently guided to the inside of the heart. Blood pressure and oxygen measurements are taken in the four chambers of the heart, pulmonary artery and aorta. In addition, contrast dye is injected to more clearly visualize the structures inside the heart.
Treatment for Tetralogy of Fallot
A child’s physician determines a treatment plan for tetralogy of Fallot based on:
- A child's age, overall health and medical history
- Severity of the condition
- A child's tolerance for specific medications, procedures or therapies
- Expectations for the course of the condition
- Parents’ opinions or preferences
Tetralogy of Fallot is repaired with open-heart surgery, either soon after birth or later in infancy. The goal of the surgery is to repair the four defects of tetralogy of Fallot so the heart can work as normally as possible. Repairing the defects can greatly improve a child’s health and overall quality of life.
The operation is performed under general anesthesia and involves:
- Closing the ventricular septal defect with a patch
- Opening and enlarging the obstructed pathway between the right ventricle and pulmonary artery with a patch
- Opening or removing the pulmonary valve if it is small